


If Loving Me Is Wrong, Then God Damn You Do It Right

by MeGaLoTrash



Category: Undertale (Video Game)
Genre: Alternate Universe - Underswap, Before Game Events, Confessions, Dom blue, Dry Humping, Ecto-Penis (Undertale), Ecto-Tongue (Undertale), Ecto-Vagina (Undertale), Ectobiology, Explicit Language, Explicit Sexual Content, Fingering, First Time, HoneyBerry, Light Angst, M/M, Masturbation, Mating Cycles/In Heat, Mutual Masturbation, Oral Sex, Pining, Semi-Public Sex, Some Fluff, Some Humor, Specifics Tags to be added when updating, Swapcest - Freeform, Underswap Alphys - Freeform, Underswap Asgore, Underswap Papyrus, Underswap Sans, Underswap Undyne - Freeform, Vaginal Fingering, Voyeurism, humping
Language: English
Status: Completed
Published: 2017-08-07
Updated: 2017-08-22
Packaged: 2018-12-12 10:04:24
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 8
Words: 20,722
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11734785
Author URL: https://archiveofourown.org/users/MeGaLoTrash/pseuds/MeGaLoTrash
Summary: Stretch is pretty sure he's going to die alone.No matter how hard he tries he can't seem to get his brother out of his head.It's wrong. So wrong. But it feels so right.





	1. Chapter 1

Despite being relatively young by monster standards, Stretch was pretty sure he was going to die alone. Currently he was perched in his bedroom window, taking long drags of a cigarette as he watched Snowdin residents get up for the day. Family units, older couples and young sweethearts seemed to make up the town, which only served to further his feeling of isolation. Stretch struck up a match to light his second smoke in the cold morning air. As he felt the vice begin to have a calming effect he let his mind wander... 

It wasn’t that he hadn’t had offers of companionship, by monster standards he was a pretty attractive guy. He’d been given the nickname Stretch from a few of his friends that he tended to tower over even when slouching. It was such a widely used nickname he wondered how many people knew his actual name. He was tall with a thin frame but he tended to hide in oversized hoodies and baggy shorts. Stretch’s facial features matched his long frame, plus a strong jaw line that some older monsters remarked he inherited from his father. Remarks like that had made him pretty self conscious, he often walked around with his hood up in unfamiliar areas. The drawstrings of his hoodie were always frayed from him nervously chewing on them. 

Despite all his self-proclaimed shortcomings, he still seemed to attract attention. He wasn’t sure what part of the ‘always tired’ look was appealing to others, but he guessed his laid back attitude made him easy to get on with. Monsters tended to be able to see past external looks and appreciate people’s characters. Stretch was a good guy deep down, he love cracking jokes and had accumulated a lot of friends all over the underground.

That was the issue though, everyone was ‘just friends’ with him. On the rare occasion he’d felt an attraction to another monster it had been a short lived fling or they’d given up and moved on. It didn’t help that biologically it was rare that he was compatible with anyone, let alone meet someone from his race. Skeleton monsters had always been rare, sitting somewhere between the human and monster race lines genetically. The war had made them almost extinct. With the underground’s population dwindling, Stretch found it hard to form an attachment when he could be left for someone more compatible. He wasn’t the type of guy to get in the way of someone else being able to start a family. 

_family_. That was a touchy subject for Stretch on the best of days. It made his leg start to bounce nervously just thinking about it. He had no memory of his mother, and the memories he did have of his father before his early demise… weren’t the most pleasant. For the most part he’d grown up without parental influence, just him and his slightly younger brother Sans. Having someone close to his age growing up was great, but his brother’s shorter stature and childlike wonder made him seem younger than he was. It had earnt him the nickname Blueberry in the underground as a kid, much to his frustration. It had stuck, but Stretch had ended up shortening it too Blue most of the time, his brother seemed to mind that less. 

Recently though, his brother had started to seem more mature. Stretch had noticed the change gradually, but more people were starting to remark on it as he gained more confidence. His brother was constantly training to be within the chance of making the royal guard. It made his smaller frame bulk up pretty fast. He was also taking on a lot more responsibility locally, and had become some kind of local hero to the younger monsters in town. Stretch could hear him now moving about downstairs, probably preparing for another day of working hard. 

Even though Blue’s recent bravado had meant the smaller skeleton was always lecturing Stretch about his lazy behaviour, he could tell his brother really did care about his well being. It was one of the reasons Stretch absolutely adored him. Blue was a kind soul, he always saw the best in everyone and went out of his way to make people happy. Stretch thought his brother was the coolest, smartest and kindest person he knew… and he was hopelessly in love with him. Stretch knew it was wrong. _so wrong_. He had spent quite a few years denying his feelings towards Blue, but he realised that was futile. Trying to ignore the fact that his brother took up almost all of his waking thoughts didn’t get him anywhere, he’d settled instead on guilt tripping himself over being a disgusting individual. In his effort to figure out why he was so attracted to Blue he had found that monsters in the past had inbred to continue their races, but that was ancient history. They were civilised monsters, in control of their baser instincts. Plus Blue would never see him in that way. Stretch had resigned himself to a life of pining after someone who wouldn't want anything to do with him if he knew how he really felt.

Only, it wasn’t that simple. The problem lately was that Blue couldn't seem to keep his hands off him. Blue had always been an affectionate monster, he loved hugs and closeness and had done since they were baby bones. Lately however his contact would linger, the hugs felt tighter and Blue seemed to find any excuse to be near him. Blue had always insisted on having a night-time story as a babybones, and they’d kept it up as a tradition. Nowadays Blue insisted Stretch came into his bed to read them. Blue would curl his smaller body around him while dozing off, making the cutest little noises. It was killing him. 

Stretch tried not to read too much into it. He tried brushing it off as platonic affection. It was all his mind and desires looking for something that wasn't there. He really tried, but when he was alone at night it was all he could think about. Stretch found his hands wandering over his slender frame at night, wishing the practised caresses came from smaller hands. He’d bring himself to climax with his brother's name on his lips, the guilt and shame hitting him when he came off the high. He knew it was wrong. He spent hours thinking about how much he loved his brother’s smile, how cute he looked when he was flustered, _how their bones fit together perfectly._. It was so wrong, but it felt so right.

“PAPYRUS! ARE YOU UP YET?” Blue’s voice came crashing through his fantasies grinding them to a halt. 

Stretch quickly put out his cigarette and sprang up from the window frame as he heard the familiar stomping coming up the stairs. He pulled his hoodie down, making sure to cover his crotch in the process. Just thinking about his brother had made his magic start to whir over his bones. It was like his body knew it had a chance of contact, a chance to hold Blue in his arms and feel him pressed into him. _pathetic_.

“MORNING SLEEPY HEAD!” Blue beamed at him after throwing his bedroom door open.

The ‘no lock’ policy in their house had originally been his idea. He wanted Blue to feel welcome to see him whenever he wanted, especially when he was younger and suffered from nightmares. As they had got older Stretch never had the heart to put one on his door, even if it made his nightly activities a lot more risky. Some of his darker fantasies had him wishing that Blue would burst through when he was too far gone to stop. Would he be disgusted? Embarrased? Aroused? _no!_ Now was not the time to be thinking like that when Blue was literally feet away from him. Treading the line between fantasy and reality was becoming a dangerous habit. 

“hey little bro, what’s got you in such a good mood unf-” Stretch was cut off by the ball of energy tackling him into a hug. He tried to stop his soul beating so hard it threatened to come out of his chest. But seeing the way Blue’s eye lights were shining with tiny Stars; it was really fucking hard.

“ALPHYS HAS AGREED TO FINALLY MEET WITH ME! THE REAL ALPHYS! HEAD OF THE ROYAL GUARD!” Blue screamed with glee wrapping his arms tighter around Stretch as he spoke.

“that’s great bro... y-you may want to change first though” he replied, trying his hardest not to let on how much their proximity was affecting him. It was embarrassing how quickly his body was responding to the most innocent of touches. 

Blue backed away from him with a shocked expression clutching at his pyjamas. It seemed in his excitement the smaller skeleton had forgotten that he was still in his night clothes. Stretch personally didn’t mind, the snug blue one piece had been a birthday present from him last year. Stretch had managed to find a shade that perfectly matched his brother’s magic attacks, Blue loved it so much he had refused to take it off for three days. Blue’s appreciation of anything Stretch did for him was just one of the many reasons he found his brother so endearing. And why it made him such a creep for his more than brotherly feelings.

“OH GOSH! IT WON’T DO, HELP ME PICK SOMETHING OUT PLEASE?” 

Before he had chance to protest Stretch was being grabbed by his hand and led to his brother’s room. As a stark contrast to the mess he called a bedroom, Blue’s room was spotless. He sat himself on Blue’s crane bed as his brother looked through his well organised closet. Everything in Blue’s bedroom was order and perfect, _just like him._ Stretch had to mentally chastise himself again at that thought. It seemed his mind was on a singular track of obsession today. He probably needed a little time alone later to satisfy his urges, he hoped it wouldn’t make it worse.

Eventually after much debate Blue had picked out a suitable outfit. He started to undress from his pjs and Stretch instinctively averted his eyes. He knew Blue wouldn’t mind him watching, he had seen everything before. But at the rate his mind was going, he couldn’t risk being caught staring. Just the thought of his brother’s pale, bare bones literally feet away from him was making him sweat. The air in the room suddenly felt very thick. Stretch’s usually carefully held together control over his feelings felt like it was slipping. Despite himself he found his eyes darting towards Blue as he finished changing. The brief glimpse of an exposed spine made him feel like he was on fire. 

“HMMM, IT’S NOT QUITE RIGHT” Blue was looking at his outfit in the mirror as he spoke. 

Blue had picked out a gray t-shirt, knee length blue shorts and a pair of black boots. He however didn’t seem happy about it, he kept tugging at his clothing trying to figure out what was wrong. Stretch thought he looked great, as always. The training Blue had been doing since deciding he wanted to be a royal guardsman was starting to pay off. He was still slight in stature, but Stretch could really tell he had a bit more substance and strength to his frame now. It took a lot of control not to imagine how Blue could easily overpower him now. 

“it’s missing something, wait here” Stretch said before going to grab something from his room.

He had managed to get his head out the gutter long enough to remember he’d purchased something special for Blue a few weeks ago. It was intended as Gyftmas present, but Stretch was sure he wouldn’t mind getting it early. He retrieved the unwrapped box from under his bed, trying to ignore the excitement bubbling up. Stretch was pretty sure his brother was going to love it, he practically ran back into his brother’s room. 

Stretch handed Blue the box with a sheepish grin, eager to know if he would like it. Stretch sat himself back on the bed as he watched his brother make quick work of the packaging.Blue’s eyes lit up when he realised what it was. Just like his pyjamas, the scarf Stretch had picked out matched his magic. Blue went to try it on, using the mirror to help him tie it perfectly. It was pretty big on him, the material flowed behind him like a cape as he examined himself in the mirror. Stretch thought he looked incredible, so he was a little taken aback when Blue turned to him with tears in his eye-sockets. 

“PAPY! IT’S PERFECT!” Blue exclaimed, immediately quelling any doubts Stretch had. 

Blue ran to embrace him as he giggled happily. Being sat on the bed meant that Blue came up higher on him for once, Stretch found himself almost winded with the force of Blue’s chest colliding with his face. He could hear Blue babbling his thanks and how much he liked it but he was more aware of how loud his brother’s soul was beating through his shirt. The steady thrum of excitement was strangely comforting, but also made that fire inside him burn hotter. Stretch tried to push the flood of intrusive thoughts away, he was not going to ruin this moment for either of them by being a pervert.

“i’m glad you like it. you look great, it really suits you” Stretch said, leaning a little further back to get a proper look at him.

Blue’s grin was practically taking up his whole face. His eye lights continued to sparkle with stars. This close Stretch could see a light dusting of blue magic on his cheeks. _Adorable_. He couldn’t help but smile too, his brother’s ecstatic energy was contagious. The smile was short lived when Blue leant in and placed a chaste kiss on his cheek, just beside the corner of his mouth. 

Stretch felt like he’d been hit with a freight train. All the feelings he’d been trying to push down came back screaming. He felt his face flush, his soul pulse, magic spark around his frame and settle in his pelvis. His magic had taken form without his permission and he could feel the familiar slick pussy materialise in his pants. _no no no_. Panic started bubbling up through the cluster-fuck of emotions he was feeling as Blue pulled away. He prayed that his brother couldn’t see his magic glowing through his clothing. 

“What’s Wrong Papy?” Blue looked genuinely concerned, but the use of his nickname in such a intimate tone made Stretch shudder. He needed to get out of there before he ended up doing something he would _really_ regret. 

“n-nothing. just let me grab my things and i’ll walk you to waterfall o-ok?” Stretch managed to get out while removing himself reluctantly from His Brother’s grasp and bolt towards his room.

Part of Stretch’s mind was screaming at him for running away, he was glad the logical part was winning out as he pushed open his door and slumped down on the other side. Stretch prided himself on being a guy with full control of his magic. He was absolutely mortified but he silently thanked whatever Gods were watching over him about forming his preferred genitalia, rather than his biological disposition. A boner was a lot harder to hide. He breathed in deep, calmed himself then dispelled his magic.

Only it didn’t go away. He frowned and tried again. Nothing. 

_why the fuck wouldn’t it go away?!_. Stretch felt the panic start to consume him. He’d never had this issue before. Even when he was really turned on he was able to get it to disappear, even if it hurt to do so. So why wasn’t it working now? Stretch was balling his hands into fists against the door as he desperately racked his brains for any idea of what was happening to him.

_oh-_

A flash of his father reluctantly explaining about monster relationships-Stretch being yelled at for not paying attention- The diagrams - how skeleton’s biology was different- what could trigger a- 

_oh no_

What could trigger a skeleton’s heat.


	2. Chapter 2

**Summary for the Chapter:**

> Didn't expect to update so soon, but here we go!  
> Please be warned there is graphic sexual content in this chapter.

The walk from Snowdin to Waterfall had been more than awkward. Stretch had tried to distract Blue by trying to get him excited about meeting Alphys. He had tried to brush of his earlier behaviour as him feeling like he was coming down with cold, and not wanting to spread it to his brother. It had almost worked, though Blue kept asking if he was too unwell to come with him . Blue wasn't entirely wrong, Stretch might not actually be ill but he was completely fucking sick.

In the lulls of silence between them Stretch tried to piece together more fragments of his memory on monster heats. It happened in a variety of ways depending on the monster, but as a rule it was always when they were comfortably settled down. Heats were only supposed to happen when a monster had chosen their life-mate; as both the monster in heat and their chosen partner had to be willing participants to reproduce. Monster reproduction only happened when two souls connected as one, and giving yourself over like that took a lot of trust and preparation. Of course there were anomalies, cases where a monster’s heat was triggered without those conditions, but why the fuck did it have to happen to him?

He couldn't let Blue know. If his memory was sketchy on the subject, he doubted his younger brother’s would be any better. Plus Blue was finally getting the chance to follow his dreams, Stretch would never let worry for him get in the way of that. There was a definite possibility that Blue was his catalyst. That his body had confused his unrequited feelings as something between them. He could never let Blue know if that was the case, he was too afraid of losing him. News like that would both upset and confuse him. Stretch knew this burden was his to bear without his brothers help.

 

“WELL! HERE WE ARE… Are You Sure You’re Going to be ok Papy?” They had Reached the crossroads near Alphys’s place without Stretch noticing.

 

“s-sure thing bro, i’ll be fine. don’t worry about me, you’ve got a big day ahead” Stretch replied trying to hide his flushed features in his hoodie a little more. 

 

“OK! I’ll Call You When I’m Done, Make Sure To Let Me Know If You Get Any Worse Though Ok?” 

 

“promise” Stretch gulped hard. He hated Lying to his brother, and he already knew his ‘illness’ was going to get worse. 

As he and Blue parted ways Stretch made sure to hug his brother hard and wish him good luck. Anything less would have been suspicious. He had the sense to put on an another pair of boxers under his shorts.He hoped to dull any sensations that innocent touches would give him, but just holding Blue close made him ache. Stretch grit his teeth and ignore the urges to return his brother's kiss from earlier. He knew he wouldn’t be able to stop himself at just one. 

After waving Blue off Stretch started weighing his options. He could head home, camp out in the shed for a few days and fob Blue off with an excuse. But just being near him would slowly chip away at his control and he could slip up. He could leave, maybe hang out at muffets and drown everything by running up his tab. While tempting, he couldn't risk Blue coming to drag him home in an inebriated state. He could barely control himself now, who knows what he’d be like with his judgement clouded and Blue angry and handling him roughly... _fuck i’m just making it worse_

Stretch was fast running out of ideas. In his desperation he thought of the one person in the underground who would know what to do. He changed direction and started towards Hotland before hesitating, he hadn’t been near the lab in years. He wondered if his former friend would harbour any resentment for him disappearing, but Undyne of all people would understand why he kept his distance. She’d experienced firsthand how degrading working under his father could be. Stretch admired how she’d managed to continue on working there even after the accident. When Stretch heard she’d recently been made the official royal scientist, he was really happy for her. Only he’d not yet built up the courage to congratulate her in person. He guessed his pressing issue was a good a reason as any to push back his fear and make the journey. 

With his mind made up Stretch made the journey through the remainder of Waterfall. He could tell the briefest of Contact with Blue moments ago was having a huge effect on him. He felt the unbearable heat from earlier return along with a constant feeling of wetness in his pelvis. Stretch could only hope Undyne wouldn’t ask too many questions before helping him. He hoped she would have something in the lab that could control the effects of the heat. At the very least he knew there would be some research papers buried away in his father’s old office. He was willing to try anything at this point.

Stretch had reached the point in Waterfall with the least amount of light; a twilight marsh with a lot of dead ends. No one was around, he had only the soft glow of his surroundings for company. His lust muddled brain was trying to get him to turn around and find Blue, or at the very least head home to take the edge off. _or just find somewhere quiet, no one is around_. Stretch stopped dead in his tracks. He tried to ignore the thought that threatened to de-rail his plan, but it was too late. Stretch desperately tried to regain his balance as waves of desire hit him hard. Looking around frantically he scrambled down a dark dead end and sank to his knees. 

Trying hard to rationalise his risky behaviour Stretch concluded that while not ideal, doing something about his pressing need was for the best in the long run. With how erratic he’d been all morning, it was probably wise to do something about it while he had the chance. Scared to make a noise, Stretch tentatively ghosted his hand under his hoodie at first. Being experienced in self pleasure as a default had it’s perks, he knew exactly where to press. He started to rub along his sensitive floating ribs, clamping a hand over his mouth to stop a moan forming. _so worked up already, shit_. 

He decided to forgo any further foreplay, Stretch let his hand travel down over his shorts to rub the sensitive flesh underneath. Thankful for the barrier of material for now, he clamped the hand harder over his mouth. Finally touching himself felt so good. He’d never gone so long from forming his pussy to doing anything about it, Every light touch sent shivers up his spine. Doing another quick scan of his surroundings to make sure no one was watching in the dark, he finally let his mind wander. 

Stretch tried his hardest to think of anything but his brother. He thought about a pretty monster he’d seen on NTT, about a drunken kiss at Muffet’s months ago, anything to make him feel less guilty. But nothing could stop him when his gaze honed in on an echo flower. A blue echo flower. His Blue…

_-They were in his room, Blue was sat in his lap as Stretch stroked his hand over the side of his brothers skull. Blue’s eye lights fluttered into stars as he leaned up to press their teeth together, grinding his pelvis down as magic sparked between them-_.

Fuck. Stretch rocked up into the flat bone of his carpals as his imagination conjured up his soul’s desires. There was no use trying to fight it any more. He needed to get off quickly. Sighing he used the hand over his mouth to draw his hoodie in further. Stretch knew it wouldn’t be long before he was too far gone to care who saw him, but for now he just wanted the ground to swallow him whole. Moving one hand back over his mouth he moved the other under his shorts for more direct contact.

The hard bone felt a little cool against the warm conjured flesh, making him hiss through his teeth. Stretch felt anxious to touch himself directly still, he opted to run his phalanges along his outer lips. Although a familiar touch, the effects of the heat were hitting hard. He cried out into his hand, too loud for comfort. Stretch decided instead to bite down on a metacarpal to dull any further sounds as he continued his exploration. The sensations were so intense it felt like it was someone else's hand, which helped his imagination take over.

_-What would Blue do if he saw him like this? Had he ever seen a Pussy before? Did he ever make one of his own?!_

Stretch groaned around the bone in his mouth as he began giving his pussy slow, gentle touches. His mind ran wild as he tried to mimic what Blue would do if he was there. If Blue wanted him like he did. He let his eye sockets close fully as he gave into his darkest fantasies. 

_-Blue’s breath was on his neck as he teased fingers over Stretch’s dripping folds. He was pressing lightly, exploring him for the first time. Stretch was starting to fall apart underneath him, panting softly. Blue leaned back, his eye lights glowing low. He made sure Stretch was looking right at him as he pressed a fingertip into his entrance-_

Just like in his mind Stretch re positioned himself to sink down on his own hand. The angle was awkward, and he was struggling to stay kneeling, but his mind made up for his shortcomings. 

_\- Blue started moving his fingers faster, face lighting up as he heard Stretch moan. He pressed further inside with each thrust, slowly growing in confidence. Stretch grabbed at his brother’s shirt, wanting more. He was pleading with his eyes and begging Blue to move faster. He wanted to let his brother know just how much he needed him-_

Stretch fell back on his haunches as he sped up the digit inside him. He pushed in a second finger to join the other, crying out and rocking into them as hard as he could. He was close already, but his body was crying out for more.

_Blue was directly above him now, thrusting his fingers in relentlessly. Stretch searched his brother’s face for any sign of his inevitable rejection but he found nothing but adoration in his eyes. Blue curled his fingers up into him so hard he was seeing stars. Stretch couldn’t communicate in anything but moans. He watched his brother’s tongue slide seductively over his teeth before he leant in further to whisper the words he needed to hear._

_“Come For Me Papy”_

 

For a moment, he was in heaven. 

 

White heat flowed through Stretch in ripples as he came with a muffled cry of his brother’s name. Rather than feeling satisfied, he felt like he’d opened the floodgates. He needed more. Reality came crashing down quickly and he realised he was alone in the dark, a dripping hand in his pants and an arousal that hadn’t gone away. _what a pathetic sight_.

Stretch cursed himself for not having the sense to think about the clean up. He felt the magic from his release slowly seeping into his bones and tried to focus enough to do something about it. He carefully removed his hand from his shorts after trying to get most of the liquid off his still conjured flesh. Even in the dark he could make out the faint orange glow of the sticky substance, the ectoplasm had a bio-luminescent quality to it. He hoped any residue left didn't show through his shorts.

Not able to think of any other options Stretch gingerly brought his hand up to lick it clean. He’d tasted himself before; in his mind he couldn’t sink any lower, which did wonders for accepting his other kinks. Something about the taste was different though, more earthy and comforting. He was getting light headed again just running his tongue over his bones, making sure not to miss a single drop. 

Cutting through his foggy mind Stretch registered a faint sound coming from his left. Jumping to his feet he quickly adjusted himself to prepare for anyone coming past. Only there wasn’t anyone there. Slightly confused, Stretch moved towards the direction of the sound, only to feel his soul drop when he realised the source of the voice. 

“-fuck-sans” an echo flower chirped quietly in the same muffled tone he climaxed with. 

 

“oh no, shit no!” Stretch felt his tone rise as he started to panic. 

 

“oh no, shit no!” came the reply. 

This time Stretch had spoken loud enough for a few of the flowers to catch it. Already on his feet he began to break into a quick stride away from the scene of the crime. He’d done enough damage already. As the echo flowers picked up sounds from each other, he had to continue his journey in the darkness with a mocking chorus repeating his anxious thoughts. It felt like the universe was punishing him for his sins.

Eventually he navigated through the rest of waterfall and into Hotland. He’d made the journey many times in his youth, but nothing could prepare him for the dread that filled him as he got closer. The the familiar sight of the looming Hotland lab flooded him with mixed emotions. _it had been so long_. Stretch briefly considered turning around and forgetting the whole thing, but he knew he wouldn’t last without external help. Calming his shaking hand he reached up and gave a firm knock on the Lab door.

No answer. _this was a bad idea_. He waited a few more minutes before deciding he’d come too far to give up now. Finding no doorbell, Stretch knocked again. He’d almost given up when he saw the large door open a crack and an uncertain voice come from inside.

“P-Papyrus? Is that y-you?”


	3. Chapter 3

**Notes for the Chapter:**

> slight warning if you have issues with medical related content. very mild, but i don't want to trigger anything if you do <3

“long time no see, doc” 

“Papyrus! I’ve told before you not to call me that… I-i never did finish the doctorate” Undyne huffed at him, opening the door further.

She stood with her arms folded in mock irritation, but there was a slight smile on her face giving the game away. The lab behind her was dimly lit but he could still make out her features. She looked a little more tired than he remembered, her long red hair was tied in a messy bun and Stretch could tell there were at least 3 pens held in there. Undyne was still wearing the same pair of thick rimmed glasses he remembered, in fact Stretch was pretty sure the dungarees and lab coat were the same too. She eventually stood aside and let him in shaking her head. 

Stretch took a few steps forward in the darkness of the lab before Undyne gave a panicked squeak and fumbled for the light switch. Doing a quick scan of the interior he was surprised to see how much had changed. The structure of the place was familiar but it felt a lot brighter. Colorful posters adorned the walls as well as a bunch of charts with pictures and strings attaching them. _messy. he would hate it_ Stretch thought before pushing the intrusion away. The lab looked so much better with Undyne’s additions, it didn’t do well to dwell on whispers of the past. 

“getting the position of royal scientist kinda trumps any lousy certificate ‘dyne...sorry by the way, i should have come sooner” Stretch turned to offer a small smile with his apology but undyne looked pretty flustered. Her eyes were downcast and a she had a prominent blush on her cheeks. Stretch felt bad, when they first met she had seemed so confident, this place had broken her. 

“I-it’s ok Papyrus, i understood why” she brushed a stray hair out of her face before giving him the briefest of eye contact “I’m sure we’ve got a lot to catch up on… b-but that’s not why you’re here is it?”

Undyne averted her gaze again as the blush darkened across her features. Stretch stood dumbfounded for a moment at her question before the realisation hit him. _she knew, was it that obvious?_. He didn't realise he had started shaking until he felt Undyne’s hands come to steady him.

“shit. it’s that bad? oh fuck! i thought you wouldn’t be able to tell. i'm so sorry-” his mouth was running faster than his mind as the thoughts came tumbling out. 

It was too much for him. The heat, The lab, and now the embarrassment. He felt tears pooling at his eye sockets. He felt like such an idiot, crying in front of his friend after not seeing her in such a long time. 

“It's ok Papyrus. I only noticed because it was so dark. Even still i only knew something was up because i've been reading up on the subject- ectoplasm is weird right?- glows the same colour as magic- and the adaptability-oh im sorry! I'm not helping, ah! Sit here i'll go make tea!” Undyne didn’t give him a chance to get a word in edgeways as she babbled nervously before sitting him down on a desk chair.

She left quickly for the kitchen, giving him some space.Stretch was thankful for the moments respite, he folded in on himself in the chair and buried his skull in his hands. Due to having a breakdown in familiar surroundings, he felt like he was a kid again, being chastised for one thing or the other. He had to remind himself again that all of that was in the past and he worked to calm his breathing. Stretch was no longer the mischievous youth. He was an adult, with a very adult orientated problem. 

Undyne returned shortly with two mugs of hot tea. She placed one in Stretch’s hands before grabbing another chair and sitting herself down across from him. At any other time this reunion would have been pleasant, they could sit reminiscing about old times. But instead the air felt thick with tension. It wasn’t like Undyne was trying to make him feel bad, the scientist sat across from him nervously fiddling with the bottom of her lab coat. But neither of them knew what to say, for fear of making it worse.

Stretch didn’t give the tea long to cool before taking little sips. He was still sniffling back tears but the hot liquid was soothing.He recognised the taste, it was something he hadn’t had in years but it was Undyne’s favourite. It brought him back to long nights where they had stayed up to finish projects. Undyne had even remembered to put a spoonful of honey like he preferred. Stretch looked up from his tea, catching Undyne’s concerned look. He gave her a small smile of thanks. 

“Feeling a little better?” Undyne asked. Stretch just nodded, still nursing the hot mug close to his chest “Oh! Congratulations by the way. Who is the lucky monster who managed to tie you down?”

Stretch sighed, he should have known this would have been the first thing any sane person would ask. He felt a tear trickle down his face. He could tell Undyne the whole story, but he couldn’t run the risk of losing a friend like her too. Or worse, she could be so disgusted she’d tell other people too. Rumours spread fast and it could get back to Blue. Swallowing hard Stretch decided to add another lie to his list. 

“t-that’s the thing ‘dyne. something's not right, i don’t have a mate” Stretch muttered.

It wasn’t entirely wrong. Even if his heat was because of Blue, they weren’t mates, and they never would be. He saw Undyne’s face change from a comforting smile to one of confusion and he winced at the inevitable questioning. 

“Oh. But that’s not- sorry, it obviously is possible, it’s happening to you! I’m so sorry Papyrus, but i’m glad you came to me for help” Undyne’s reassuring smile was back and Stretch felt a little relief wash over him.

“so...you can help?” Stretch asked. 

“Yes and no. I can’t reverse the effects of the Heat but i do have something that may help. I developed it for Queen toriel to use for members of the royal guard, so it’s completely safe. Though it’s never been tried it on a skeleton monster- I’m sure it will be fine!” Undyne got up from her chair before gesturing him to follow.

Although apprehensive Stretch trailed behind Undyne as she led him into a sterile looking room. He’d never been able to go in these rooms in the past, they were usually occupied by ‘patients’ or as he and Undyne referred to them ‘Gaster Guinea-pigs”. The room now looked more like a drop in clinic, there was a few counters with various medicines, and a hospital style bed in the center of the room. Undyne had already begun sifting through a draw to find what she was looking for as Stretch wondered what he’d got himself into. Turning back to him she had retrieved three syringes filled with a translucent liquid. Stretch shuddered, he should have known it would involve needles. 

“The serum will stabilizes the effects of a heat. The guards take it when they’re away from their mates while on duty. It lasts a few hours but-” Undyne had averted her gaze again as her blush creeped back over her face.

“-When it wears off at night the heat will hit hard, it’s meant to be used so when the monster is back with their mate they can… take care of it together. In your case, you’ll have to take care of it yourself by- y-you know” 

Stretch felt himself recoil more into his hoodie. He knew exactly what she meant, having been doing it about an hour ago. Thankfully Undyne didn’t want clarification, she took his silence as an answer and continued. 

“I’m sorry i can’t make the problem disappear Papyrus but at least this way you’ll be more in control of it? We can start now if you want, i can show you what to do” 

Stretch answered with a nod, not trusting his voice to be steady right now.

“Can you lie on the bed please and- sorry- if you could p-pull your shorts down enough to expose the top of the ecto-flesh i can show you where to inject” 

He froze for a second as Undyne turned around, giving him some privacy. It wasn’t that he didn’t Undyne completely but being exposed like this seemed to make his problem all the more real. Not wanting to give himself long enough to lose his nerve, he’d come this far after all he jumped up onto the hospital bed. Thankful for wearing baggy clothing, the shorts and boxers were easy to manoeuvre downwards. He moved them down far enough to expose the area around his ilium and watch as the area around him was filled with a soft orange glow. Undyne had turned back around and was preparing the needle with a steady hand even if she was sweating nervously. 

It was mortifying. 

“S-so you press the needle into the flesh here. What it does is release endorphins that mimic -ahem- stimulation. It’s a slow release so it shouldn’t feel intense but you may experience some tingling-” 

Undyne inserted the needle as she was talking, trying to distract him as much as possible from the situation. Stretch covered his mouth with one hand while the other was holding his shorts down. He tried to focus on her voice not on his overwhelming embarrassment. 

“-it will stop it being as distracting as it is now. Normal things shouldn’t bother you as much but any direct stimulation will override the effects. So don’t worry about waiting if you are able to… be alone at all” Stretch had managed not to make a peep but feeling the needle leave him made him whimper in discomfort 

“Ok we’re done, i’ll let you get dressed.”

He didn’t need to be told twice. Stretch pulled up his shorts and sat up quickly, making him wince as he caught where the needle had been a second ago. He wasn’t able to feel the effects of the serum yet but even the non sexual touch from Undyne inserting the needle had made him feel on fire again. He felt like he’d sunk to a new level of low.

“thanks ‘dyne. i owe you one” Stretch finished getting dressed and got up off the bad, keen to get as much distance from him and the room as possible. 

As they walked back the the lab entrance Stretch heard the familiar jingle of his text tone. The noise made both him and Undyne jump from their already frayed nerves. Stretch muttered a quick apology before going to read the text. It was from Blue, he was finishing up and wanted to know if Stretch was still around to walk home with him. Part of him wished they had more time to spend catching up but honestly he was thankful to have an escape from the awkward situation. 

“I have to go, brotherly duty calls” Stretch moved towards the lab exit with Undyne ready to see him off. 

“Oh how is Blue? He must have grown so much since i last saw him! I wonder if he remembers the time he got lost so lost in Hotland it took us about 3 hours to find him?” Undyne chuckled into her hand at the memory.

Stretch remembered it well. When they finally found Blue he’d managed to get himself stuck in the middle of a vent puzzle. The image of himself and Undyne yelling at each other while getting stuck themselves by going the wrong direction had him laughing along as well. It was easy to forget about the good times they did have together. Stretch felt a glimmer of hope over being able to repair their former friendship.

“heh- i’ll remind him later. he’s all grown up now, i’m actually going to pick him up from a meeting with the head of the royal guard”

“He’s seeing captain Alphys? W-wow, what a lucky guy” Undyne’s fins flattened to her head as she spoke, an obvious sign she was hiding something.

Stretch guessed it was probably a crush if his memory was correct on her tell, but he thought better over pressing her about it. Undyne had already done so much for him today, he could leave the teasing for a later date. 

“Oh, don’t forget these!” She handed him the other two syringes in a plastic case. “Just inject them as i showed you. Give yourself plenty of time in between the doses to let the Heat run it’s course. Sorry i don’t have more, but if it’s still around in a few days please come back. I’m not sure how long heats last without a mate. S-sorry again Papyrus”

With the vial tucked safely into his jacket pocket he gave Undyne a brief hug, careful to keep his sensitive ecto-flesh away from direct contact. She smiled and waved him off with another reminder to call her if he needed anything else. 

Walking back through waterfall took a lot less time than it had earlier, and Stretch made sure he walked very fast through the area of his previous transgression. He wasn’t sure if he could handle any more embarrassing situations for the day, but he prepared himself for the inevitable. The magic serum seemed to be taking an effect, walking was no longer making him painfully aroused from the friction. He felt his head start to clear a little, so much so he could pick up some distinctive voices from up ahead. 

“Thankyou SO MUCH For Today Captain Alphys, Ma'am” Stretch heard Blue call out to his companion. He was so happy it was going well, he decided to hang back behind a convenient stone wall. Blue didn’t need his un-cool older brother cramping his style right now. 

“I keep telling you Blue, just Alphys is fine. Now, keep up with those exercises i taught you-” Stretch heard the gruff voice of Alphys reply, to his surprise she seemed a lot more laid back than he imagined her “-Oh and be sure to sort out your other issue before our next session”

Stretch didn’t intend to eavesdrop at first, but he found himself acutely aware he was hearing something he shouldn’t be. _what was blue’s ‘issue’?_ Had he been hiding something? Was Stretch so wrapped up in his own problems he’d neglected to notice something was wrong. 

“I Will! Thank You For Listening Alphys. You’re Right, I Should Just Be Honest About How I Feel” Blue was shifting from foot to foot as Stretch felt his soul drop. _how he feels, did blue like someone else?! oh no_

“Right! And hey if they reject you just call me up, I’ll kick their punk ass!” Alphys laughed.

That confirmed it. Stretch was in already in terrible situation because of his lust for his brother. And he’d just found out Blue was going to confess his feelings to someone else. If souls could break, his would be shattered into a million pieces.


	4. Chapter 4

**Summary for the Chapter:**

> two updates in one day? i must be mad.  
> I didn't like where i left it, i'm going to be busy for a while soooooo...  
> hope you enjoy :)

Blue was full of energy as they walked home. Stretch had been able to hide in his hoodie as he listened and added occasional questions about his time with Alphys. He was glad his brother was so occupied, he didn’t want Blue to see him fall apart. He tried not too, but he kept thinking about what he had overheard. Who was this monster that his brother had kept secret? How did they meet, how far had things got? _what made this monster better than he was?_. 

Stretch almost stopped walking at that thought. He always knew the day would come where Blue would find someone, he had no right to be jealous over something he could never had. As he continued to listen to his brother’s excited chattering he realised how little time they may have left together. Blue was moving up in life, he eventually join the royal guard and now he had a love interest to share his life with. Blue didn’t need his creepy older brother hanging about and dragging him down. 

Blue wouldn’t see it that way though. Stretch could tell even now as they walked and talked Blue was constantly involving him and waiting to hear his approval. He hoped he hadn’t been too absent minded in the conversation so far, he was so wrapped up in his thoughts he forgot to live in the moment. If Blue really was going to be leaving him, he shouldn’t be wallowing in his sadness. He should be savouring every moment they had together now. Mind made up, he pulled his hood down and engaged himself in the conversation fully.

“You Should Have SEEN Her Papy! Alphys Is Amazing! CAN YOU BELIEVE SHE BEAT UP BOTH OF THEM?” Blue’s pitch was increasing as he relayed his day, particularly about the fact that Alphys could take down two of her guards at once.

Stretch could believe it. He had memories of when he worked in the lab and a then young trainee of the royal guard had been brought to them in a critical condition. Alphys had bit off more than she could chew at the time, she was barely alive. But she still came in with a smile on her face. Actually, thinking back he remembered Undyne had partially attentive of the young warrior, it must have been the start of her crush. 

“she sounds great bro, did you get a chance to show off your fighting skills?” Stretch asked, eager to hear how his brother fared. 

“Not As Much As I Wanted To, She wanted To Talk More About Why I Wanted To Be In The Royal Guard And Get To Know Me A Little-” Stretch tried to keep his expression neutral, he wanted to know more about what they talked about but he knew he couldn’t ask. “- But I Did Show Her The Blue Attack You Taught Me, She Thought It Was Really Cool!”

“heh- i just taught you the basics, you’ve got a much better handle on your magic than me bro. just wait and see, you’ll make the royal guard in no time”

“Thank You So Much Papy!” Blue squealed, coming in to hug him from the side as they walked.

Stretch was thankful that the serum had calmed him down enough so he didn’t freak at the contact. Blue gave him a big squeeze, he really was getting strong, before lessening up. He didn’t fully detach himself but rather continued walking with his arm linked around the one Stretch had shoved in his hoodie. 

The act of casual intimacy was both comforting and harrowing for Stretch. On the one hand it reminded him that even if Blue did have someone in his life, it was unlikely to affect the lifelong bond between them. On the other, he couldn’t help but yearn for more. As they passed a few monsters on the way home, he wondered how they looked to outsiders. To people who didn’t know them, they could be mistaken for a happy couple in a loose embrace. He’d be lying if he said it didn’t hurt thinking about Blue doing this with someone else. 

When they arrived at the house Blue went barrelling inside and straight to the kitchen. Stretch decided to flop down on the worn green sofa in their living room. It had been a very tiring day already and he could do with a nap now the effects of the heat were starting to lessen. Stretch drew his hoodie back over his head as he lounged on the sofa. He could hear the familiar Clatter of Blue moving about and found his eye sockets start to feel heavy before fully closing. 

 

*************************************************************************************

 

“SURPRISE!” 

Stretch was jolted awake by a very enthusiastic Blue shoving a plate of food near his face. 

“They’re Called Tacos! Alphys Told Me I Should Try This Recipe AND I DID IT!” Blue beamed at him.

Stretch gathered a bit more of his bearings before going to take a bite out of one of them. The taste was...indescribable. Trying not to let the repulsion show on his face Stretch continued to eat the taco as his brother waited with baited breath for his review. 

“they’re great bro, better than anything i could ever make” Stretch tried to be as honest as possible to hide the lie. It was true though, his idea of cooking almost always involved him not being the chef.

“Of Course They Are! I Think You’ll Find Brother, My Skills Match Yours In Almost Every Way ” Blue giggled before taking a bite of his own taco. 

Stretch could see the moment when Blue realised he might have been exaggerating the truth with his earlier compliment. His face screwed up at the taste, but other than that it seemed that he was trying not to let on. Stretch quickly tried to think of a way to distract him from the less than appealing meal. 

“i still think i could win in a tickle fight, even the magnificent sans is no match for my fingers of death!” Stretch pretended to laugh like an evil villain as wiggled his fingers for effect. Even if he could never have Blue the way he wanted, he was going to be the best big brother he could be. 

“You Think You Can Beat Me? You’re On!” Blue slammed his plate down and started towards him. Stretch had to leap up from the couch to try and de-escalate the situation. The serum may be working but he’d been asleep for a while, and he couldn’t risk Blue actually _touching him_.

“i was only kidding blue, let’s just sit down and-”

“-NO! My Honour Has Been Challenged! I Must Defend It! Mweh Heh Heh!”

Blue divided towards him and Stretch barely managed to jump out the way and make a break for the stairs. Blue continued to chase him, giggling happily at the game. Despite himself Stretch found he couldn’t help but crack a smile as he dodged the never ending swipes. Blue got hold of him at the top of the stairs, almost trapping him in a bear hug. In an impressive move he managed to slip out of their position and made a pretty good show of sliding down the banister and out of Blue’s reach. Stretch look back at his Brother when he landed and felt the smile fall off his face.

Something about the way Blue was looking at him was different. Blue was still stood in the same position he’d been in when he’d had Stretch in his grasp. It was a subtle change, but his expression looked darker, almost dangerous. Stretch found himself frozen to the spot as Blue came down the stairs two at a time. His smile looked almost sinister as he launched himself at Stretch, tackling him to the ground. 

“Give Up Papyrus, I’ve Caught You” Blue laughed as he leant over his startled brother. 

The laugh may have seemed light hearted, but there was an under current of something else. Stretch had landed flat on his back when Blue tackled him, meaning Blue was currently kneeling while leaning over him. To make matter’s worse the fall had made his legs open at an awkward angle, and Blue had taken it upon himself to position himself between them. There was literally an inch between their pelvises. _oh no_

Stretch couldn’t control the hard thumping in his chest as the effects of the Heat started to come back into his conscious. Blue was close enough to him to be able to feel the warm breath coming from his continued laughter. Surely that meant Blue could also feel the warmth coming from between his legs. Stretch tried to raise a hand to cover his face only to have Blue pin it above his head.The lurch forward meant they were pressed together fully now, and the heat sensitivity meant Stretch could feel every single bit of delicious pressure from the body above him. _oh fuck_.

Stretch was completely powerless pinned under his younger brother. Blue kept giggling as he used the hand not pinning him down to continue his tickle assault. Stretch was trying not to make a sound, but he couldn’t stop his body writhing from both the tickling and the incredible sensation of having Blue _so. fucking. close._ . Even through both layers of their clothing he could feel Blue’s solid form pressing into him. It was better than even his wildest dreams. It had been so long since they had rough housed like this, he couldn’t help but notice how much stronger Blue had become. He had such a firm grip, an overbearing presence, and powerful thrust in his hips. 

_wait. what?!_

Either his mind was playing a cruel trick on him or he really had felt Blue thrust his hips up to meet his own. It had to have been an accident. It had to have just been a nothing more than an innocent bump. It had to be… _but what if it wasn’t?!_

“Do You Give Up Papy?” Blue chuckled darkly above him. 

There it was again. It felt like a definite thrust that time, there was no way he could be imagining it. Blue’s tickling hadn’t stopped but it had lost its former vigour. Stretch had moved his other arm to sling over his face, wanting to do anything but look at his brother above him. He was terrified Blue would see right through him and know how turned on he really was. 

“Don’t Hide From Me Papy, I Want To See Your Face When I Win” 

Blue stopped tickling him for a moment to move his other arm off his face and up to where the other was pinned. He was leaning into him fully now and Stretch couldn’t resist the urge to look at him any longer. He really wished he hadn’t. Blue’s face was completely flushed, his eyes were glazed over and Stretch could see the glow of his tongue in his mouth. He found himself rocking into Blue’s pelvis before he could stop himself, and he would have sworn he saw his brother’s expression show a flicker of lust. Even if it was in his head, it no longer mattered, they had to stop. Now. 

“please don’t blue ah-” Stretch couldn’t help the moan that followed his plea. _it felt so good, oh stars_

“Oh Papy! I Pushed It Too Far! I’m So Sorry I’m A Terrible Brother!” Stretch’s voice seemed to break through whatever trance Blue was in as he let go of his arms and pulled him into an apologetic hug. 

“No, please sans i’m-uhh” Stretch tried again to get Blue to move off him but all ended up doing was palm fruitlessly at Blue’s clothing.

“I Love You So Much! I’m So Sorry I Hurt You” Blue hugged him tight, wrapping his arms around him and pushing their bodies even closer than before. 

It was too much, Stretch’s body was responding to the direct stimulation just like Undyne had warned. He tried to muffle his whimpers into his now free hand as Blue held him tighter but refused to _keep still_. Stretch needed to get out of there. He needed to get to his room, the bathroom, outside, _anywhere that wasn’t here_ before this escalated any further. Stretch could feel Blue shuffle against him again and he thought he would finally be free. But instead he felt something else press against the sensitive ecto-flesh of his now dripping pussy. Something hot and hard, but definitely not bone. 

The worst thing that could ever happen in this moment, actually fucking happened.

He came. 

The serum coursing through his body masked some of the intensity but there was no mistaking the heat that exploded in his pelvis. _fuck fuck fuck_.His hand was still over his mouth and he used it to bite back a moan. He could feel Blue tense up on top of him and for a moment he was sure he’d been figured out. But he didn’t say anything. Neither of them did. The silence seemed tick on forever before Blue leaned back from him, a even more prominent blush across his features. He looked embarrassed, but not angry. That was somehow worse. 

When Blue finally moved off Stretch he stood up quicker than he should have, the result made him feel really dizzy. Blue had caught his fall and was using his own arms to steady him as he looked up at Stretch with a face full of confusion and concern.

“Papy, I-I’m Sorry, Wait!-” 

It was too late. Hearing Blue think his disgusting behaviour was something he should be sorry over made something inside him snap. Instead of doing the sensible thing and talk things through Stretch panicked and did something he swore he’d never do to Blue.

He ran.

He could hear Blue calling after him after he turned around and immediately went to open the door. He knew he should take responsibility, stay and finally face the music . But he just couldn’t bear to see Blue’s face go from admiration to disgust when he realised how much of a disgusting being his brother really was.

The snow was falling as heavy as the tears running down his cheeks. Night was falling and the snow made it hard to even see a few feet ahead of him. He didn’t care.

He just needed to live in denial a little while longer.


	5. Chapter 5

It was getting darker and darker as Stretch continued to trudge through Snowdin forest. The snow was falling thick and making it hard to both see and move forward, but he didn’t care. He just needed to put more distance between him and his problems. He was acting on instinct only, he didn’t dare think logically in case it tore him apart. Tears froze on his cheeks as he carried on moving further into the forest. He knew it was dangerous and he could end up lost; but those possibilities seemed like a blessing in his current state. He was such a fucking idiot. 

Part of him had wanted Blue to chase after him, his brother could easily outrun him, but Blue didn't follow. _probably wants nothing to do with you_ Stretch cursed, breaking out into a run again just to try and distract himself from the creeping dread. The pain and ache of forcing himself to move against the weather was preferable to emotional pain that he couldn’t get rid of. He was so wrapped up in his head he didn’t notice the stray branch before it was too late. He tripped up, landing face first in the snow and hearing the distinctive sound of breaking glass as the vials Undyne gave him broke in his short pocket.

_of course that happened, this day just needed to get worse._

Tears had been falling from his eye sockets since he’d left the house, but this was the first time he’d felt himself actually sob. Tremors racked his frame from the intensity of convulsions and he found himself curling into a ball instinctively on the cold, hard ground. In an instant Stretch no longer felt like an adult, but rather a scared child, too overwhelmed with the raw emotions he was feeling. He couldn’t clearly remember the last time he’d broken down like this, it had been so long he could almost mistake the cold of Snowdin’s floor with the cold floor of the lab in Hotland. That thought just made him sob harder. 

He felt like he’d been crying for hours when he finally stopped shaking. The emotions were still as fresh as they were before, but his body could no longer keep the tears flowing as heavily. He raised up slightly on his haunches, trying to adjust his eyes enough in the darkness to figure out where he was. A small form of relief washed over him as he was greeted with a familiar sight. A few feet away from him stood a large door covered in vegetation, a testament to how old the structure was. The entrance to the ruins of the old capital had been sealed for years and yet, somehow, Stretch had managed to form a friendship with someone on the other side.

Stretch walked towards the door before he quickly turned around and slumped down, making an audible thump as he reached the ground. Having left the house in a hurry he’d completely forgotten his phone, and had no idea of the actual time. He doubted his friend would be around this late, but it was worth a shot. He reached back to knock on the door, only to hear a faint knock coming from inside. He was a little startled that his friend was there already, but decided to play along anyway.

“Who’s there?” Stretch tried to keep his voice as light as possible; considering he’d been baling moments he wasn’t very successful.

“Pasture” was the muffled reply. 

“Pasture who?” Stretch frowned, he hadn’t heard this one.

“Pasture bedtime, isn’t it?” 

Stretch laughed, really laughed. His friend behind the door always had bad jokes, but this was terrible even for him. He could hear the smooth baritone coming from behind the door as his friend laughed along. For a moment, he was happy. _if he was that close, he probably heard you crying like a baby bones._. The happiness didn’t last. 

“Forgive me for being rude, but you don’t sound too good my friend." 

Stretch could hear the concern in his friend’s voice, his fears confirmed. This was new territory for them. He’d been coming here on and off for a few weeks ever since he found out there was someone actually living somewhere he’d assumed was abandoned. Their talks so far had only consisted of light hearted conversation and sharing of jokes. He didn’t even know the monster’s name.

“sorry, you had to hear that. it’s been a rough couple of days” Stretch replied. 

“I don’t mean to pry, but is it your first time?” there was a pause while Stretch struggled to understand the question before they clarified in a quieter voice “-your first heat i mean-”

“how did you-”

“-Sorry! I didn’t mean to make you uncomfortable, friend. When you’ve lived as long as i have you tend to notice the change in people pretty quickly-” his friend sighed softly before continuing “-I was fortunate enough to be mated once, but I still remember how agonising my first heat was. Oh, where are my manners? Congratulations, I’m sure you’re making someone very happy.”

“no i’m not-” Stretch didn’t mean to sound so sharp, but he was fed up of the assumptions making him more aware of what he didn’t have “-i’m in heat, but i don’t have a mate.”

 

“Oh dear, I am sorry. I had assumed you and your brother had sorted out your differences and-”

 

“my brother? wait, what the hell are you talking about” Stretch could feel the panic rise in him. _was he that transparent?_. He guessed since all this monster knew about Blue was from his stories, no wonder he’d figured out his obsession. But his friend thought he and Blue were _mates?!_.

"I’m sorry i assumed you’d finally mated with… Sans was his name right? The way you talk about him all the time I thought you were both finding it difficult to adjust from brother to mate. Are you saying you don't feel that way about him?” Stretch could feel the embarrassment in the other monsters tone, he’d made them feel uncomfortable. He thought about brushing it off, spinning another lie of denial but… he was tired. And he needed a friend.

“no- i mean- yes. oh god i can't believe im telling you this. i love him that way, but he doesn’t feel the same. i’m pretty sure the heat is because of that, one more way to punish me for being in love with someone i shouldn't, it's so fucked up. i’m sorry, i’ll understand if you don't want to talk to me any more” Stretch could feel the tears falling again as he spoke. 

Surprisingly, he didn't feel worse from confessing like he thought he would. Something about the anonymity of having the door between them made him finally open up While he felt the dread of judgement, finally being able to talk about everything eating him up was a bit of a relief. However, the silence from his friend was not reassuring. He had blurted a lot of things out though, so he tried to stay calm and wait for them to process. Although he’d said it was ok if they wanted to leave, he held onto the hope that his friend would stay. Even if they thought he was a piece of shit. Anything was better than being alone in his thoughts right now. 

“Did you ask him how he felt?” his friend asked. 

“I kind of ran away before he had chance to say anything” Stretch grimaced at the confession, he still couldn’t believe he’d actually ran. _pathetic, and a coward on top of that._.

“I see. I can tell you don’t want to tell me what happened to make you leave, but did he seem mad or angry at you at all? i know it’s hard not to project your feelings onto Sans, but Try and remember what actually happened."

Stretch went to answer in the affirmative, of course Blue was mad at him. But he stopped as the monster’s words really sunk in. _had blue actually been mad at him_. Despite trying to push the evening's events out of his mind for the past hour, Stretch tried to remember what Blue had actually done. Scouring his memories he kept coming up empty for examples of Blue being mad, annoyed or anything negative. The worst he could find was the confusion that was over his face before he ran, just after Blue had been on top of him. After Practically fucking him into the living room floor. Even he had to admit, it was hard to think Blue was completely repulsed by him if he’d willingly done _that._

“no, he erm- didn’t seem mad” Stretch replied before getting too lost in his thoughts. He could tell his friend was onto something but it couldn’t be-

“-So Sans wasn’t mad? Don’t you think it’s strange that you’ve been spending more time together and then you go into heat. It’s very rare that a monster goes into heat without even a potential mate, friend. Is there a possibility, even a small one, that he could share your feelings?”

Stretch could feel the logical side of his mind finally take over and analyse what he couldn’t deal with emotionally. The lingering hugs, the wanting to get near him, the closeness and the lack of repulsion on Blue’s face before he left. _fuck_. The crush on the other monster, it hadn’t even crossed his mind that Blue could have been talking about him. How could he have been so blind to that possibility when the signs were plain as day? Even if it was only on a subconscious level, Blue’s soul was calling out to his. That’s why it had felt so right when they were together, that’s why Blue hadn’t pushed him away, that’s why he’d gone into heat in the first place. Their instincts had won over logic, sensed a suitable mate and acted accordingly. Stretch wasn’t an anomaly, he’d just been too mad at himself to see anything else. 

He needed to go home.

“i-i think i need to go, i can’t believe i’d been so stupid.” He needed to face his fears and talk to Blue. Even if his brother didn’t want anything to happen between them, the possibility of Blue hurting like he was made up his mind. 

“I understand, don’t be too hard on yourself in such a confusing time. Listen, I'm an old man. I know what it's like to have happiness in your grasp and have it taken away. It really makes you appreciate the chances in life. I know it may not be ideal, and the fear of judgement from others over your previous relationship may be tough. But it’s worth a shot if it means you can both be happy together.”

Stretch could hear the faint sadness in the other’s voice, and he desperately wanted to return the favour and listen to his friend’s worries. But they both knew that he might have a limited window of time to repair the damage he did from running out. Plus if he stayed, he would probably lose his nerve. Stretch pushed up from the door to stand, wiping his eye sockets again for any stray tears before saying a final goodbye. 

He set off for the home he shared with Blue with a little more confidence in his step. He knew he couldn’t dwell in the past any more, that there was no point trying to deny his feelings, he had to try to move forward. Hopefully his brother would want them to move forward together. Stretch knew he was getting ahead of himself, that his hopes could just as easily end up being crushed, but he couldn’t help the flutter in his soul. There was a chance that his feelings weren’t unrequited. It was crazy to think about it after years of denial, even though he knew he shouldn’t get carried away he could feel he was smiling. 

 

The house was dark and quiet when he finally arrived home. Even in his eagerness to get home, it had still taken him quite a while to make the journey in the dark. _Blue is probably already asleep_. Stretch thought about waking his brother for a moment, but upon seeing that Blue’s door was close, he decided against it. A good night’s rest would probably be good for them both so they could gain some perspective. Stretch doubted he’d sleep too well with his emotions all over the place, but the exhaustion from his late night trip was a pretty persuasive feeling. 

With his mind made up he snuck up the stairs and into his bedroom, careful not to make a sound. Sleep was starting to sound like a more amazing idea by the second. Stretch kicked off his shoes and flopped down on the bed without bothering to get undressed. Ready for the exhaustion to take over he slipped his sockets closed with a yawn.

 _blue was above him, predatory smirk on his face while Stretch was pinned beneath him. Arousal evident Blue slowly ground his hips into the willing body beneath him-_

Stretch snapped his eyes open. With everything that had happened he had almost forgotten about the pressing need of his heat. It seemed in the moment of silence his mind had decided to remind him of his constant arousal in a very graphic way. Groaning, he guessed the effects of the serum were really starting to wear off now, making his heat impossible to ignore. He knew it was risky doing anything with Blue probably on high alert, but he knew he wouldn’t be able to sleep without taking care of it. With a double check to make sure his door was closed and there wasn’t any movement in the house, he slipped a hand into his shorts.

Stretch grimaced slightly over how wet he was already, he guessed some of the liquid was from his unexpected orgasm earlier. Knowing he needed to be quick, he didn’t try and stop the memories from earlier continue to replay in his mind. 

_Blue was pretending to still be tickling him, Pining Stretch arms above his head as he experimentally thrust forward. Stretch was moaning, wrapping his legs around his brother’s hips and matching his thrusts-_

Stretch knew his imagination was changing details to what he wanted to happen, but he didn’t care. Not needing to prepare himself he eagerly plunged two digits into his entrance, gasping at the contact. Moving his head to the side to bite on his pillow, Stretch let himself re-imagine what happened.

_  
Blue still had him pinned but their clothing was gone and his cock was buried deep inside him. Stretch was trying to hide his face as he moaned like a whore. Blue grabbed his skull, forcing Stretch to make eye contact as he growled out a command._

_“Don’t Hide From Me Papy, I Want To See Your Face When You Cum.”_

__

Stretch worked his phalanges faster as he imagined Blue’s cock fucking him instead. He just needed to stay quiet a little longer, he was so close. 

_Blue pulled out only to slam back into him hard, making Stretch cry out. His eye sockets were filling with tears as the sensations became too much. Blue noticed, but only increased his pace, his hand firmly around Stretch’s mandible as he drove him to completion._

_“That’s It, Cum For Me... Papy”_

_“...Papy”_

__

Stretch didn’t notice the slow creak of the door before it was too late.

“Papy?”


	6. Chapter 6

Over the years Stretch had planned for this moment.

He knew that living in a house without locks meant it was a huge risk to do anything sexual at all. His plan had always been to make sure to listen for even the smallest of noises. He’d practised dispelling his magic and stopping at a moment's notice. If all else failed and he did get caught, he’d come up with a million lies from feigning illness to making up a mystery partner he was thinking of.

But with Blue actually in the room with him, he realised none of his plans were going to work. 

Blue hadn’t made a sound since saying his name. Stretch was well aware that he still had a hand in his pants, and he couldn’t get rid of his magic even if he wanted too. _but he really didn’t want too_. The fact that Blue hadn’t seemed embarrassed, yelled at him, or made any plans to leave had peaked his interest. Despite the panic over being caught, Stretch found himself looking in Blue’s direction to try and get some answers.

_holy shit_

Even in the dark of his bedroom he could make out Blue’s features. It helped his face was lit up by the soft glow of magic currently dusting his cheek bones. Blue seemed a little reluctant to meet his gaze, his eyes lights darted up and down Stretch’s body, settling anywhere but his face. However Stretch could still make out the stars in his eyes when Blue looked up at him. To have his brother’s attention like that, it felt amazing. 

The tension in the air was thick. Blue’s face still looked uncertain, even if it was mixed in with other emotions. Stretch had to try and focus, not get carried away with what he wanted, but let Blue take the lead. If Blue wanted to leave, he’d let him. If Blue wanted to talk he’d put everything aside and listen, fuck the heat. If Blue wanted to do more than just talk… _not now_ Stretch tried to keep calm even though his hand was still in his pants, fingers brushing against his throbbing pussy. 

Noticing the faint blue glow in his brother’s pants didn’t help.

“C-Can I Come In?” Blue asked finally, shifting on his feet a little. 

Stretch tried to push away the feeling of his soul bursting with joy at such a simple question. He couldn’t let himself jump to conclusions, but he also didn’t trust his voice to sound anything but lustful right now. He gave what he hoped was a clear nod before shuffling up the bed somewhat and going to take his hand out his pants-

“No Don’t- P-Please Don't Stop… I Want To Watch. I Won't Do Anything More, But...Please” Blue interrupted, his voice barely above a whisper. 

Stretch froze, his hand stilling as soon as Blue spoke. Everything previously had all been speculation, part of him was still clinging onto the thought that Blue would be disgusted with him. But there was no mistaking what his brother had just said. Stretch wondered if Blue knew exactly what he was asking, but one look at his brother as he moved to the end of the bed made that notion disappear. There was no mistaking the desire written across Blue’s face; his eyes sockets were lidded, and his tongue was already formed and hanging heavily in his jaw. Stretch knew he should have clarified what Blue wanted, what he meant by ‘anything more’, and if he actually wanted to do this and wasn’t just humouring him. But he was terrified to say any more, he wanted it so badly it hurt. He could feel his mind start to go fuzzy as the effects of the heat took over and he placed his hand back over the dripping mound in his shorts. 

The air hung heavy as he started to slowly stroke a digit over his outer lips. Having Blue in the room while he touched himself felt a lot less awkward than Stretch anticipated, he had to remind himself again to take it slow. Even if it felt like every nerve ending in his sensitive flesh was on fire. He continued to stroke himself lightly, deliberately avoiding the urge to slip his fingers inside. He wanted to ease them both into whatever this was between them slowly. On a stroke upward he managed to bump his clit and couldn’t stop himself from letting out a little moan. Stretch clasped his free hand over his mouth in shock, half expecting Blue to chastise him for making such a lewd sound. Blue instead moved closer, half climbing onto the end of the bed. 

“Can You Take Your Shorts Off?” Blue sounded strangely calm, like he was in some sort of a trance. 

Stretch knew he probably shouldn't, something about being so exposed would cross a line they couldn’t go back over. They needed to talk things through, but they were too far gone already. Stretch felt like he was on autopilot as he shimmied his shorts down. He tried to hide his dripping pussy behind his hand initially, scared to expose himself all at once. Blue was moving fully on the bed now, seating himself in between Stretch’s spread legs. Blue was transfixed, Eye lights never leaving his crotch and his expression willing him to continue. Stretch could feel himself turning a brighter shade of orange as he moved his hand away slightly so Blue could see him fully. 

“Its So Pretty… P-Please Show Me More ” Blue whispered.

_how could he refuse?_

Stretch moved two of his phalanges towards his entrance, watching Blue’s reaction as he started to move in and out. Blue was more flushed than he’d ever seen him. He had one hand pulling at the scarf around his neck to loosen it and one hand moving close to his own crotch. The glow in his shorts was brighter and Stretch could see Blue was trying really hard not to buck up into his hand. He wanted more than anything to tell Blue he wanted to see him too, but he didn't want to scare him off. Even if Blue was obviously interested, asking him to join in just felt too direct. Also he probably wouldn’t be able to get the words out right now if he tried. 

_Maybe he could convince him another way?_

The fleeting notion gave Stretch a little more confidence. His brother was obviously interested, why not give him a real show? He pulled his fingers out almost fully then slammed them in hard, moving the hand over his mouth away slightly so Blue could hear how good he felt. He rocked against his hand as he moved his fingers inside against his inner walls, letting out little moans and whimpers. It felt so good to finally allow himself to give into his urges without being worried about being caught. He just needed to entice his captor to join in.

A quick glance at Blue confirmed his plan was working. His brother had his hand firmly on his crotch now and was moving his hips in time with Stretch’s fingers. Stretch could still his soul fluttering with nerves but he felt encouraged to keep going if it was having such an enticing effect on his brother. He withdrew his fingers momentarily to come up and circle the bundle of nerves at the top of his pussy. Watching Blue go from barely holding back to grasping at his cock through his pants sent shivers down his spine. Blue moved his hand to his zipper before he glanced up at Stretch for confirmation that it was ok. He nodded enthusiastically and continued to moan just in case he needed a little more encouragement. 

_...wow_

He heard Blue gasp when he finally freed his erection from the confines of his pants. Stretch could have made an educated guess it would have been the shade of his brother’s blue magic, but actually seeing it made him whine. He wanted to replace the fingers inside him with Blue’s cock so badly, but the slither of logic left reminded him that they _really_ needed to talk before doing that. For now, just seeing Blue starting to pump his hard length was enough to turn Stretch into a whimpering mess. Stretch couldn’t help but notice Blue’s practised technique, his brother was definitely not as inexperienced in self pleasure as he originally thought. Flashes of Blue touching himself when he was alone filled his already over active imagination as he thrust his digits back inside his pussy. He knew he wouldn’t be able to last much longer at this rate, he hoped Blue wasn’t far behind. 

Blue’s smaller hand was only just able to wrap around his length, making Stretch twitch in anticipation of how it would feel inside him. Blue’s moans started to fill his room to, Stretch couldn’t believe his brother’s voice could sound like that. Blue’s naturally cheerful tone was still there, but there was a lower, guttural tone of barely restrained lust. Blue steadied himself on Stretch’s extended leg following a particularly loud moan, the force of his ministrations knocking him off balance slightly. Their connection was electric, like magic was sparking between them, and it felt amazing. 

“Papy. I..I’m...Close Ah-” Blue cried out, working the hand around his cock frantically. He looked up to Stretch as he spoke, his eye lights glowing blue as he panted heavily. Stretch couldn’t believe he was lucky enough to have someone so beautiful fall apart in front of him.

“it's ok bro, ah me t-too” Stretch replied. He could feel himself reaching the heights of climax so strongly it felt like all the bones in his body were shaking constantly. He positioned the fingers inside himself to stroke against his spot, seeing stars like the ones in Blue’s eyes as he neared release. 

“You Look So Good, I Can't- Ah! PAPY!” Blue tightened the grip on his leg and threw his head back. Seeing the magical release spurt from his brother’s cock was enough to make him cum as well. He stilled the fingers inside himself and pressed up into the hard bone of his metacarpals, the power of his climax almost making him black out. 

Blue was still leant against his leg as they come down from their high, his breath was tickling Stretch’s tibia. Coming through the post orgasmic haze made the reality of what they had just done really sink in. It wasn’t like they could pretend it hadn’t happened either, Stretch had a hand over his still present arousal and a glance at Blue showed he was in a similar situation. Stretch thought that was a little odd, he thought it was only a heat that made an arousal persist after climax. He had so many questions, but as time went on he found it harder and harder to make a sound. 

His brother broke the silence first.

“I’m So Sorry Papy- I Should Have Spoken To You First, My Heat Is Driving Me Crazy” Blue confessed, moving his hand off Stretch and allowing him to close his legs by shuffling out the way.

It took Stretch a moment to process what Blue had actually said. Initially he thought Blue had figured out he was in heat, and it was having an effect on him but- _he said ‘my’ heat- what the fuck?_ -

“-your heat? what are you talking about blu-”

“Oh Stars! I Should Have Told You! I’ve Been In Heat For A Few Days Now, I Thought It Would Go Away If I… Took Care Of It. But It Just Made Me Want You More!” Blue’s Eye sockets started tearing up as he continued “I Didn’t Want To Tell You As I Thought You’d Hate Me, But Having You Pinned Under Me And Writhing Around Just Drove Me Crazy, I’ve Wanted You For So Long- I Shouldn’t Have Taken Advantage-” Blue was starting to tear up. Stretch sat up on the bed further, forgetting modestly and moving his hands to clutch as his brother before interrupting him. 

“-you could never- fuck blue. i wanted this. i’ve been trying everything i could to hide how i felt about you and that i was in heat, a-and now you’re telling me you’ve been suffering too? shit, i can’t believe all this time....” Stretch tried to keep his voice steady, but he was in disbelief.

When the idea entered his head that his brother wouldn’t reject him, he thought Blue may just be starting to feel the same way. He would never in a million years have anticipated Blue’s confession, to hear he’d been wanting him just as much, and now to know his Brother was in heat too? His soul started swelling with love. The universe didn’t hate them, they had chosen each other as mates. They just had been too worried about each other’s feelings to realised.

Stretch couldn’t help it, he started laughing.

Blue had looked confused for about a second before he started laughing too, coming to the same realisations. What started as a little titter soon turned into them fully cracking up while leaning on each other for support. So many feelings and memories started to fall into place, all the feelings he’d been battling with suddenly felt right. Stretch knew tears were falling down his face, but they weren’t painful. It was like a huge weight was being lifted off them both and they were finally able to see each other clearly. 

“Oh Jeez, We’ve Both Been Pretty Stupid Huh?” Blue brought a hand to his face to wipe, still giggling like baby bones. 

“you can say that again...” Stretch shifted a little, he wanted to be sure of Blue’s feelings before anything else but he was still nervous to ask. “so, this is really what you want? you definitely want… me?”

“Oh Papy-” Blue moved closer to him as he spoke, half climbing into his lap and bringing his arms to circle round him “- I’ve Never Wanted Anything More, I’m So Happy You Feel The Same Way”

Blue embraced him fully then. Stretch could feel through the tightness of his grip just how sincere he was. Blue was never one to toy with people’s emotions or be dishonest, so he knew his brother meant what he said. Stretch felt him start to pull away pretty quickly, he was going to protest but Blue’s expression made him pause. 

“Can I Kiss You Papyrus?” Blue’s eye sockets were lidded, and the muted expression of desire was hard to hide with their faces so close. 

“oh god blue, you don’t have to ask hn-” Blue cut him off, clanking their teeth together harshly.

The magic spark they’d felt before was back the moment their teeth connection, making Stretch whimper against him. Blue wasted no time in pushing his tongue against his slightly open mouth, eagerly seeking out Stretch’s tongue to entwine with. Blue tasted a little sweet, like he expected, but the strength behind Blue’s kiss reminded him against that his little brother wasn’t as innocent as he thought. Blue’s body felt hard and warm pressed against him. The slight grinding of his brother’s hips made him realise that while there first kiss was as sweet as he dreamed off, they were both still very much in heat.

Just thinking about what that could mean in the immediate future made Stretch groan more into the kiss, gripping Blue tighter to him. They eventually separated, both panting slightly before Blue moved off his lap. Stretch knew what he wanted, he knew Blue wanted him too, so he was a little confused by him leaving. Not wanting to push him though, he resigned himself to the fact that they may need to take things a little slower than he wanted. 

“That Was Amazing, But I Think We Could Both Use Some Rest, How About We Call It A Night?” Blue got up to leave, pretty casual about the fact his pants were still undone.

_and he was still hard._

“Are You Coming? My Bed Is Bigger And Erm- Cleaner” Blue asked, his hand extended for Stretch to take. Stretch was on his feet and lacing their hands together quickly as he followed his brother’s lead. 

He didn’t need to be asked twice.

**Notes for the Chapter:**

> see? told you i couldn't keep it agnsty for too long :P  
> thankyou for reading, hope you're enjoying it so far!   
> Pretty sure there will be two more parts btw, i'm not stopping at 6 :)


	7. Chapter 7

Stretch awoke with a bit of a jump, having not really meant to fall asleep in the first place. He could see the sunlight trickling through the curtains into a bedroom that wasn’t his. He could see Blue still asleep next to him, his form entangled in the sheets. Memories from the night before were trickling back slowly as his mind started to kick into gear. After what had happened in his room they had initially moved to Blue’s room with the intention of getting some much needed rest. Instead they had stayed up a little longer, mostly talking; but the pressing need of both their heats had meant they had been unable to resist a few heated make out sessions. Just remembering the ways Blue kept moaning into his mouth while grinding against him made him clamp his legs together instinctively.

Their heavy petting would have escalated further, had they not both been almost passing out from exhaustion. With the way Stretch had woken up entwined with his brother, he wouldn’t have been surprised to learn they had drifted off half way through a lazy kiss. He tried to ignore his stirring arousal for a moment longer. He wanted to try to recall some of the more important details from their conversations last night. One particular conversation stood out near the end of the night, after it became pretty clear the heat was only getting more intense 

_  
“You Do Know The Heat Probably Won’t Go Away Until We’ve… You Know- H-Had Sex” Blue Had Been tracing a hand over Stretch’s skull as he spoke. They had been talking and kissing, most likely for a few hours, and Blue had ended up slightly on top of him with his femur wedged between Stretch’s legs. Both of them incredibly tired but neither of them were able to stop. Even just kissing felt amazing, and the undercurrent of something more was getting harder and harder to resist._

_“h-how did you know that?” Stretch was confused, he knew his brother was less naive than he initially thought, but details on monster heats seemed a little advanced. His brother was just full of surprises._

_“We Do Have UnderNet You Know!” Blue’s entire skull was lit up with magic over how hard he was blushing “I Wanted To Be Well Informed On Advanced Dating Techniques- J-Just In Case”_

_Hearing his brother confirm he’d been thinking about sex, enough to actually go out his way to look it up, made him groan and lightly grind into Blue’s leg . He would have given anything to have walked in on that scenario, especially if Blue had been worked up for_

_“so, you’ve never been with anyone?” Stretch had to know. No matter how much he wanted to be Blue’s first, he also wanted to know if Blue had any experience so he didn’t rush or pressure him._

_“-No. Nothing Serious Anyway. I Couldn’t Be With Someone Else When All I Can Think Of Is You”-_

Stretch felt himself shiver at the memory. Blue had gone on to tell him that there was no pressure, that he didn’t want Stretch to feel pressured even if they were in heat. Stretch had to remind him he was the one who came on the living room floor just thinking about it. Blue had giggled and kissed him more, whispering a few i love yous before they fell asleep. 

He was pretty sure that conversation would live with him for the rest of his days. Weather Blue’s way of speaking was purposefully romantic or just matter-of-fact it didn’t matter. Stretch had to bite his tongue at the time, almost begging Blue to take him immediately, but he knew they needed at least some rest. They were treading in unfamiliar territory even if the heat was making them both unbelievably horny. 

Their shared lack of experience made them both pretty nervous, but Stretch knew he was dangerously close to snapping and asking Blue to fuck him senseless. He knew they were moving fast, but it didn’t feel that way. Blue was his best friend, and now possibly his mate, to finally not have any secrets between them just felt right. He sighed happily and snuggled into his sleeping brother further. The shift in position made him realise just how wet he already was, his lack of pants making his femurs feel slick.

_of all the time for blue to be the one sleeping in…_

Stretch thought about whispering softly to see if Blue would wake, but decided not too. Seeing his usually energetic brother so quiet was a sight he wanted to enjoy a little longer. He would have described Blue’s sleep as peaceful, if it wasn’t for the little whimpers telling him otherwise. That and the sheet that covered them was tented quite comically, Blue’s heat was _hard_ to ignore. Stretch tried not to laugh internally at his own joke, still wondering about what to do. He didn’t want to do anything to Blue that they hadn’t done consciously, but that didn’t mean he couldn’t have a little fun waking Blue up.

Moving a little more onto his side Stretch re positioned himself so he was between Blue’s skull and his clavicle. He purposefully made his breath heavier so it would ghost over the sensitive bones of Blue’s cervical vertebrae. He could see Blue’s form shake slightly from the light stimulation and he unconsciously leaned his skull away to give Stretch better access. Stretch let his tongue snake out and gently lap along the ridges. He had discovered how sensitive Blue was there last night and he planned to put that information to good use.

Sure enough it wasn’t long until his gentle teasing was drawing a few moans from his sleeping brother. Stretch could never tire of hearing Blue’s voice like this, he increased the pressure of his tongue to see if he could pull out more noises. Blue started huffing and writhing under him, and Stretch could see his hips thrusting slightly against the air to gain a little friction. He really wanted to touch him, but he didn’t want to venture there without permission. If he could just be a little more patient Blue would wake up and hopefully be more than willing to continue. 

Stretch moved down a little more, licking along the parts of Blue’s clavicle that the loose tank top exposed. He lavished attention and kisses on his sleeping brother, savouring his taste and his reactions. He could tell Blue was starting to gain consciousness, so he upped the ante slightly. Moving his mouth back upwards he lightly bit down in between the bone, giving Blue a jolt of pleasure and he was rewarded with a more coherent groan.

“morning sleepy head, do you want me to stop?” Stretch asked in between licks. He knew the answer, but he wanted to make sure. It was all so new he didn’t want to risk messing it up, even if that meant checking in repeatedly. 

“Mmm Good Morning Papy Mwe-” Blue Moaned when Stretch bit down lightly again, arching his spine up into him “-P-Please Don’t Stop, Touch Me M-More It Feels So Good” 

Stretch wasn’t sure if it was the heat or his brother’s sleepiness that made him ask so directly, but he was more than eager to make a few tentative steps forward. He continued to tease at Blue’s sensitive spots and brought a hand up under Blue’s shirt to give one of his floating ribs a playful tug. The reaction was instantaneous, Blue responded by arching into his touch and crying out. The noise sent a jolt of desire to Stretch’s Pelvis and he shifted his position so he could start moving down Blue’s body. 

Stretch moved Blue’s shirt up to expose his rib cage and latch his mouth onto him. Any awkwardness he felt over his hunched over position was lost when he heard how much Blue was enjoying it. Stretch moved his hand lower, teasingly stroking along the way before coming to rest near where Blue’s erection was tenting his shorts. Looking up at Blue as he moved his hand closer he waited to see if there was any signs of Blue wanting him to stop. He didn’t expect Blue to grab his hand and place it on his cock, moaning at the contact. 

_fuckkk_

If Stretch thought between his legs felt wet before, he was wrong. Blue taking charge like that did things to him he couldn’t describe. His confidence wavered slightly but he wrapped his hand around the hot magic, pumping up and down a few times. Blue bucked against him and screwed his eye sockets closed, moving his hand to fist at the sheets. Encouraged by his brother’s reactions Stretch leant over him fully on all fours and pulled down the waistband of his shorts. Seeing the pulsing organ so close and uncovered gave him an idea. If Blue would let him, he wanted to put his mouth to better use. Changing his position again he moved so his mouth was inches away from Blue’s cock, hoping to make his intentions clear. 

“Papy, Y-You Don’t Have To Do That” Blue tried to reassure him and bring him back up, but Stretch could tell it wasn’t because he didn’t want too. As usual, Blue was trying to put him first. 

“i want too, let me do this for you bro, i really want to make you feel good” Stretch purred, stroking his brother’s ilium as he spoke “tell me to stop if there’s anything you don’t like ok?”

Stretch looked back at Blue long enough to see him nodding. Stretch’s breath was ghosting over his brother’s cock making him twitch in anticipation. Stretch extended his tongue out to lick around the head of Blue’s cock before taking the tip into his mouth. He may have been a little hasty, Stretch didn’t anticipate their inexperience. Blue’s hips buck upwards reflexively and he almost choked around him. Trying to keep calm he concentrated his magic into forming a pseudo throat to better accommodate Blue. Blue gasped out in pleasure when he was successful, the new sensations were hard to comprehend. 

“P-papy Hah! It’s AH! So Good- P-Please Can I-I Touch You Too?” Blue asked after Stretch had moved up and down his length a few times, enjoying how much Blue writhed underneath him. 

Stretch was torn; he wanted to focus on Blue, but his body ached to be touched. He shuffled his hips back up toward Blue so he could reach him better, thankful Blue couldn’t see how flushed he’d become. Being on all fours with his hands currently occupied meant he wasn’t able to hide how fucking wet he was. Blue stroked a hand up his femur reassuringly before moving up towards his dripping pussy. He heard Blue hiss through his teeth as he admired him, making Stretch slow on his cock slightly. He panicked for a second that Blue might be put off, before he felt a feather light touch graze across his outer lips. 

Blue’s touch was soft and exploratory, but Stretch was so worked up he couldn’t help but moan around his length at the feeling. He could tell Blue was trying to mimic how he’d seen Stretch touch himself the night before, he could feel a few phalanges stroking him all over before one digit dipped near his entrance. Stretch was torn between moving himself back into Blue’s hand and focusing on the cock in his mouth. Either way he couldn’t stop whimpering from how much he wanted everything Blue had to offer. He guessed Blue was enjoying the vibrations of his moans as he heard the other cry out before he thrust a finger fully inside him. 

Blue’s hand may have been smaller than his but it felt amazing to have a part of his brother inside him. Stretch was thankful at this angle Blue couldn’t see his wide eyed expression as he tried to focus on the cock in his mouth. Both of their movements were a little sloppy and messy, but it didn’t matter, it felt so good to finally be touching each other. Stretch started to curl his tongue around the head of Blue’s cock and increase the suction in his mouth. At first he thought Blue didn’t like it as he went quiet, so he lifted off to ask him if he was ok. He didn’t expect Blue to launch himself at him, flipping their positions so Stretch was on his back looking up as his usually sweet brother.

_he didn’t look sweet now_

“I-I Just Want To Try Something Ok?” Blue had spoken in a low voice, running his hands over his brother’s ecto flesh.

Blue had taken advantage of Stretch’s open legs and sat himself in between them. Stretch feel the heat coming off his cock with how close they were, it was driving him crazy. Blue was palming himself softly waiting for Stretch’s response with a hungry expression. Blue could do anything to him right now, he’d agree he wanted him so much. He whined out what he hoped sounded like a yes, seeing Blue’s grin turn into a smirk as he brought himself closer. Stretch was loving seeing this new side of Blue, he felt like putty in his hands.

Blue had brought their pelvises close enough to touch, but rather than going for the prize and penetrating him, Blue started to rub his cock on the outside of Stretch’s pussy. Both of them cried out upon connecting so intimately, Blue had to steady himself by slamming a hand down beside them and fisting the sheets. Blue started to move his hips to grind them together and Stretch felt himself jerking up to meet him It felt so good, he could feel Blue getting slicker with his juices on every pass. When Blue nudged the head of his cock against his clit, Stretch lost a little more of his self control and hooked a leg behind Blue to bring him closer.

Blue was growling at him and breathing heavy as he rutted against him. Stretch could see how far gone Blue was already, his mouth was parted and he could see glimpses of sharp fangs. Seeing this side of Blue reminded him no matter how sweet he seemed, his brother was still a monster and it was _so fucking hot_. Despite the primal urges overwhelming Blue, He was still able to hold back from actually penetrating him. Stretch pushed aside his last shred of anxiety in order to let Blue know exactly what he wanted. 

“saaaaannns, please -oh fuck, p-please fuck me- i need you inside me-ah!” Stretch couldn’t believe how needy he sounded, but didn’t have a chance to get too embarrassed. 

His begging was rewarded, Blue he drew his hips back to re-position himself. He let go of one of Stretch’s legs to guide his cock inside, both of them gasping when the head of his dick slipped in. Even though Stretch was obviously enjoying himself, Blue hesitated before moving in any further checking over his face for any cues that Stretch was uncomfortable. A weird pang of pride passed through him before he nodded at Blue To continue.

A flash of brighter light in Blue’s eye lights was all the warning Stretch got before Blue pushed himself in further. Feeling his brother inch into him was unlike anything he’d ever experienced, Stretch couldn’t hold his voice as he cried out in pleasure. Blue was concentrating hard on not being too hard or fast, but Stretch could hear the little whimpers of pleasure as he felt the tight heat suck him in. When Blue Was fully seated neither of them could keep still with how hard they were panting. Stretch was writhing so much he wasn't surprised to feel Blue pin one of his hands to the bed to steady him. 

“I Love You Papy, Ah- I-I Really Love You” Blue whispered in between pants.

Stretch wasn’t sure if it was the overwhelming feeling of being filled by Blue, Or the declaration of love that made tears gather in his sockets, but he’d never been happier. He sat up balanced on one arm as he brought Blue’s skull to his to kiss him hard. He was a mess of drool and tears but Blue didn’t seem to mind, kissing him back and moving inside him making them both moan into the kiss.

“l-love you too- ah, please i need you- ah! please blue” Stretch knew his speech was nonsensical but he was too far gone to care.

Blue loved him. He loved Blue. That was all that mattered.  
“Well… Since You Asked So Nicely Papy” Blue smirked at him again before drawing his hips back and slamming into him hard.

Stretch should have known from Blue’s training he was strong, but within seconds of the brutal pace he was practically sobbing again with how good it felt. He thought about trying to stop his moans so he didn’t embarrass himself, but Blue was being just as loud as he thrust into him. Blue Had fallen down onto his arms a little, bringing their rib cages closer together now Stretch was practically laying flat. Blue couldn’t quite reach his mouth at this angle but that didn’t stop him lavishing attention with his tongue on every exposed bone he could reach.

He was close already, just hearing Blue’s moans would have been enough but with all the other sensations it almost felt too much. Stretch felt Blue pull out of him slightly before moving Stretch so one of his long legs was draped over his shoulder. Stretch cursed under his breath, the new angle meant Blue was further upright and more in control of his thrusts. Blue was hitting a spot deep inside him on almost every pass as he gripped him roughly. Stretch tried to speak but it just came out as a tangle of moans as he cried out, cumming hard all over his brother’s cock. 

He heard Blue howl before hilting himself and spurting all over his insides. Just the feeling of being filled up completely by Blue had Stretch moaning again, prolonging his already intense climax. He could hear Blue still panting hard, never really stopping his thrusts causing their magical release to mix and trickle out of his pussy. He felt amazing, but even through the cloud of heat induced lust he didn’t want it to stop. He’d had a taste and he wanted more, knowing how long Blue could keep training gave him some hope. 

Blue's rest didn't last long, he pulled himself out of Stretch only to sit back and pull him forward into his lap. Stretch yelped a bit, trying to re organise his limbs before Blue pulled him close clanking their teeth together. The kiss was hard and sloppy, both of them whispering sweet nothings in between gasps of air. Stretch could feel Blue’s erection hadn't dissipated in the slightest and he couldn't help shift his hips to line Blue up to his entrance again.

He doubted either of them would want to stop anytime soon.

**Notes for the Chapter:**

> thankyou for reading!  
> i have one more chapter planned, sorta like an epilogue set a little in the future- wrapping a few bits up and probably some more fluff! hope you've enjoyed it :D


	8. Chapter 8

**Notes for the Chapter:**

> thankyou all for reading so far! All the comments and messages i've been getting for it are really appreciated, hope you enjoy the last part <3

Stretch shuffled the papers in his hands, trying to make sense of some of the illegible lab notes Undyne had given him. A few empty packets of cigarettes and discarded mugs littered the desk he was working on. He was back in the Hotland lab, he’d been coming here almost daily for the past few weeks, and he was working in a room that had started to look like his own. Since Blue had started his royal guard training with Alphys, he found he had a convenient amount of time each afternoon to drop in and help the royal scientist with her workload. Undyne kept trying to persuade him to take up an official position, but he insisted that he already had a sentry job to keep down. Plus after all she’d done to help, and how discreet she’d been about it, it was the least he could do.

The last few weeks had flown by in a blur; an amazing, world changing blur. After Spending the better part of three days working through their heats together, he and Blue had become closer than he ever thought possible. The sex was incredible, there was no doubt about that, but it was the moments in between Stretch really cherished. He and Blue had talked over some things; he’d apologised over and over for running away, but Blue had reassured him saying the only reason he didn’t follow was because he had almost ran himself. Stretch finally confessed to how long he’d been in love with Blue, and Blue scolded him in between kisses for not telling him sooner. They even talked about how other people would re-act to them being together, Stretch was glad that for now they were keeping it to themselves. They both wanted their relationship to develop without the harsh scrutiny from others who may not understand. He thought about mentioning his friend behind the door who had been so understanding, but thought against it, he’d just have to take Blue there one day. 

Even though their relationship was in its early stages, Stretch couldn’t believe how well everything just fell into place. Initially he had been worried about the haze of the heat passing and things becoming awkward between them, but that wasn’t the case. He was surprised how familiar they felt, but then he guessed it was down to knowing each other pretty well already. Small things changed around the house; Stretch made a little more effort in keeping his room cleaner now Blue was sharing his bed some nights, and Blue had become a little more lax on his ‘no smoking in the house’ policy once he really understood how much it helped calm his nerves. The time they spent together no longer had an undercurrent of tension, and Stretch found himself sleeping a whole lot better with Blue’s warm bones next to him. 

Even outside their home their interactions felt better; Stretch had initially worried people would notice but the changes were so subtle only they noticed the positive effects. Blue insisted on visiting him every morning at his sentry station when he was out on patrol, usually bringing some food for breakfast. He didn’t lecture Stretch on his eating habits as much any more, Blue even bought him some pastries from muffets as a sort of ‘2 week anniversary’ gift. Stretch had positively beamed over how cute the gesture was, especially as Blue had gone out of his way to a place he was vocal about disliking. Stretch had suggested that they went on a semi public date in waterfall that night, though he had blushed furiously when going near the location of where his heat had first hit him. Blue had managed to worm the story out of him, and instead of getting mad he decided that he wanted to try out the discreet location together. Being quiet was a lot easier with Blue’s scarf muffling his cries. 

Stretch heard Undyne knocking on the door before he snapped back to reality. The papers he was working on had been disregarded and his tea was cold.. He shook his head before turning to speak, he hoped Undyne hadn’t noticed his far away look.

“nearly done with these ‘dyne, well with what i could read any ways. got anything else for me before i go?”

“No that’s all, s-sorry i’ve been away all morning. But i have some good news!” Undyne beamed at him from the doorway.

She’d been away from the lab when he’d got there, leaving a chicken scratch note on being back soon. Stretch was about to ask her what it was when he felt his phone go off. Undyne gestured for him to answer, he took his phone out his pocket to see a message from Blue. With a quick check to make sure Undyne couldn’t see his screen he opened the message. He knew Undyne would probably be the first person he told about them but, he didn’t want to risk her seeing something she shouldn’t.

_Home! :-P How Long Are You Gonna Be?_

Stretch quickly replied telling Blue he was wrapping up before turning back to Undyne. 

“it’s just blue asking when i’ll be back, what’s the news?” 

“Well, the word from the capital is the queen has acquired the 6th human soul! With only one more to find and the research we’ve begun on human souls; we’re that much close to freedom! Isn't that great?” Undyne exclaimed.

She was literally shaking and Stretch couldn’t help join in the excitement, going over and pulling his friend into a congratulatory hug. This was huge news. With the barrier gone and monster kind free he and Blue could have a chance for a whole new life together. From what he knew of humans, most of them knew nothing about monster customs, so they wouldn’t know what he and Blue had was outside the norm. They had a chance to be happy, and he could explore the world with his mate. He couldn’t believe how quickly his life was turning around. 

Hearing his phone go off again he finished his hug with Undyne and went to check his phone. She continued to chatter about all the news she’d heard in the capital and how they could improve their research. Stretch was only half listening as he saw another message from Blue. He was so glad he’d had the sense to turn away again.

_Don’t Keep Me Waiting ;-)_

The message was simple enough, but the picture that came with it had Stretch fighting to stop turning completely orange. The top of the picture had his mouth hanging open lewdly, tongue formed and dripping onto him. Stretch saw that Blue had gone through the trouble of removing his pants, and seeing that the the tip of his cock was leaking fluid Stretch felt his magic re act almost instantly. He needed to get home. _Now_

“o-okay, if we’re done here i should get going. need to, erm, pick up some s-stuff for dinner-heh” Stretch was already making his way out the room as he spoke pausing before he got to the main door “s-see you tomorrow yeah?”

“You’re such a bad liar Papyrus!” Undyne laughed and rolled her eyes at him “So, when do i get to meet them? You obviously like whoever this is a lot if you’re still trying to hide that you’ve found someone.”

Undyne had he hands folded over her chest as she finished teasing him, she had small surge of confidence at having the upper hand. Stretch tried not to panic, he wasn’t ready and he wanted to ask Blue before he told anyone. Keeping his breathing calm he tried to think of an answer. He didn’t want to outright lie, especially not to Undyne, so he opted to tease her back instead.

“i’m sure you’ll meet them soon, maybe we can double date with you and captain alphys-” Stretch started to head out the door, practically feeling how hard Undyne had blushed from that comment “-see ya later!”

Stretch didn’t have time to gloat on flustering his friend, he walked as fast as his legs would carry him to where the Riverperson’s boat docked. The Boat ride felt like it took forever. He just wanted to be home now, enjoying whatever his brother had planned for them. He practically leaped out the boat when they reached Snowdin and power walked his way to their front door. He must have looked happier than usual, as he got a few waves from the local residents as he passed them. He smiled back, no longer envying them. What he had was amazing.

“Wow, You Got Home Quickly” Blue grinned at Stretch when he opened the door, already waiting for him in the living room. 

Stretch quickly closed and locked the door behind him before Blue was on him, pinning him against the door and dragging him down into a kiss. Blue ground himself against him as their tongues met, the fact that Blue hadn’t put his shorts back made Stretch moan against him louder. Blue continued kissing him as they moved back towards the couch, he made quick work of taking Stretch’s clothes off, pausing only when Stretch made a whimper at taking his tank off. 

“So Beautiful Papy-” Blue Sat back on the couch before taking off his own shirt “-Please I Wanna See All Of You”

Stretch felt his soul flutter upon seeing Blue’s naked form, his brother looked incredible. He hesitated for a second but eventually stripped his last piece of clothing, blushing more at how exposed he was. His pussy was already formed, it had been a while and he felt pretty wet. From his position on the couch Blue moved his hands away and replaced them with his own, gently playing with the sensitive flesh to get him to relax. Stretch expected Blue to want to move to the bedroom, but instead he felt himself being pulled into his lap.

It was a little awkward at first with trying to position his longer limbs around Blue, but it worked out with Blue’s support. Both of them gasped out when he sank himself down on Blue’s length, Blue was gripping him hard trying not to thrust up into him yet. He let Stretch set his own pace as he let himself adjust from the minimal preparation. 

“You Feel Incredible Papy” Blue moaned into his clavicle as Stretch started rocking his hips “I Love You So Much”

The unprompted praise made him shudder, a reaction that wasn’t missed on Blue. He smiled up at him with Stars in his eye lights as Stretch started to move on him properly. Both of them started to breathe heavier from how good it felt, but neither of them went to look away. Something about this position felt really intimate, and with the way Blue was being so open with him made him tingle all over. They’d just started but already it felt like they weren’t going to last long. Stretch guessed that this may not be the only time they would be intimate tonight; when it felt this good it was hard to get anything else done. 

“Sans- ah god! ” Stretch ground his hips down for effect, making Blue’s cock hit his most sensitive spots “- i love you too, so so much”

He picked up the pace slightly, moaning as Blue repositioned his legs so he could meet his thrusts. The air seemed hot and heavy as neither one of them wanted to break the proximity, he could feel sweat forming but it just made it easier to slide against each other. Blue was still trying to keep eye contact, but his eye lights had gone hazy as he struggled not to give into the feelings of pleasure. Stretch still couldn’t believe the beautiful monster below him was really his lover. _and his mate_

“Y-You’re So Amazing Papyrus, You Look So Good Like This-" Blue cried out, a string of moans in his praises "Wowsers P-Papy! You’re Gonna Make Me Cum Alread-Ah Don’t Stop!” 

Blue grabbed Stretch’s hips and started to slam up into him. Stretch was already close but hearing Blue talk about him like that pushed him to the edge. He bounced on his brother’s lap harder as he felt himself clamping up around him. Blue kept singing his praises as he came inside him, continuing to thrust and ride them both through their climax. Eventually he loosened his grip on Stretch and let him collapse against him, still joined together. Their mouths met in a lazy kiss, Stretch thought he was going to burst with how happy he felt. 

It might be wrong but feeling Blue’s soul pulsing so close to his own, Stretch no longer cared. It was right for them.

**Author's Note:**

> thankyou so much for reading!! I hope to update pretty regularly, if you have any comments/feedback i'd love to hear it! This will be my first 'longer' story, so i hope it goes ok! you can also find me on tumblr @MeGaLoTrash


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